1. Field of the Invention
The present invention relates generally to a reverberation sound producing apparatus and more particularly to a reverberation sound producing apparatus in which a reverberation sound substantially same as that obtained in the natural world is produced by an electric circuit.
2. Description of the Prior Art
In the art there is already proposed a reverberation sound producing apparatus or a reverberation sound generating apparatus in which an electric signal is applied through an electric-mechanical vibration converting element to one end of a mechanical vibration system such as a spring in the form of a mechanical vibration and then an electric signal is derived through a mechanical-electric vibration converting element from the other end of the spring. With the above mentioned prior art apparatus such a type of conversion is easily affected by an external mechanical vibration, and if the length of the spring is determined, the time period of a reverberation sound is fixed. Further, the frequency characteristics of the spring become constant in accordance with the diameter of the wire forming the spring, the diameter of the spring and a material making the wire of the spring, and consequently the frequency characteristics can not be changed from the outside thereof.
In addition to the above apparatus, there are proposed apparatus which employ a distribution factor, concentration factor and a magnetic delay line, but they can not be free from defects similar to the defects mentioned as above.
Recently, there is proposed an apparatus in which an electric charge transferring device is used to set a delay time period suitably and to produce a reverberation sound. However, the reverberation sound which is produced by an electric circuit is somewhat different from a natural one, because a natural reverberation sound such as, for example, that obtained at an audition room, a concert hall or a reverberation room has such characteristics that it has a long delay time interval for a low frequency component and a short delay time interval for a high frequency component, while the reverberation sound produced by the apparatus using the electric charge transferring device or element, mentioned above, has a constant delay time interval determined by an external control signal regardless of the frequency of an input signal.